Interface regulation via bidentate π-chelators for high-performance perovskite solar cells

Abstract

Surface defects at the interface between the perovskite and the hole transport layer (HTL) inevitably result in significant surface recombination and unfavorable energy level alignment in perovskite solar cells (PSCs). Identifying surface modifiers with enhanced binding affinity to perovskite materials is crucial because of the effective passivation effect. Here we show that the 7-azaindole molecule featuring two active sites acting as an intermediate layer at the perovskite/HTL can not only strongly passivate defects through bidentate chelation, but also enhances intermolecular π–π stacking with spiro-OMeTAD, giving rise to effective carrier extraction and favorable energy level alignment. Under the synergistic influence of dual functionalization, the PSCs modified using 7-azaindole achieved a power conversion efficiency (PCE) of 24.63%, and the stability of the encapsulated devices is also greatly improved. For perovskite interfacial engineering, the use of π-conjugated molecules with two reactive sites emerges as a prospective chemical strategy to enhance PSCs' efficiency and stability.